KR20220156092A - Linear groove formation method and grain-oriented electrical steel sheet manufacturing method - Google Patents

Abstract

To provide a grain-oriented electrical steel sheet in which linear grooves are formed on a surface of a metal strip with a desired groove width and furthermore excellent in magnetic properties. Forming a resist film on at least one surface of the metal strip, then irradiating the resist film with a laser while scanning in a direction transverse to the rolling direction of the metal strip to remove the resist film from the portion irradiated with the laser, Then, an etching process is performed on a portion of the metal strip from which the resist film is removed to form linear grooves, wherein the resist film contains an inorganic compound at 20% by mass or more in terms of solid content, and the metal On the strip surface, the laser has an elliptical beam shape in which the ratio of the major axis diameter to the minor axis diameter is 5.0 or more, and the beam diameter in the scanning orthogonal direction is 10 μm or more and 100 μm or less.

Description

Linear groove formation method and grain-oriented electrical steel sheet manufacturing method

The present disclosure relates to a method of forming linear grooves on a surface of a metal strip, and a method of manufacturing a grain-oriented electrical steel sheet using the method of forming linear grooves.

Grain-oriented electrical steel sheets with excellent magnetic properties are mainly used as materials for iron cores of transformers. In order to improve the energy use efficiency of the transformer, low core loss of grain-oriented electrical steel sheet is required. As one of the techniques for reducing core loss of grain-oriented electrical steel sheets, a method by surface processing of steel sheets is known.

Iron loss reduction technology by surface processing of steel sheet is to reduce iron loss by introducing strain to the surface of the steel sheet by a physical method and subdividing the width of the magnetic domain. One of them is to form grooves on the surface of the steel sheet by etching. There is a way to do it. Specifically, a coating material for forming a resist film is applied in a pattern on the surface of a steel sheet before a forsterite film is formed using a gravure roll or the like, and then the portion where the coating material for forming a resist film is not coated is electrolytically A method of forming grooves on the surface of a steel sheet by selectively etching using a method such as etching is known. According to this method, the iron loss of the grain-oriented electrical steel sheet can be reduced by subdividing the magnetic domains on the surface of the steel sheet by forming the grooves.

By the way, it is known that the magnetic properties of a grain-oriented electrical steel sheet having linear grooves formed on the surface thereof are largely influenced by the shape of the linear grooves. The deeper the depth (groove depth) of the linear grooves in the sheet thickness direction, the more magnetic poles are generated on the wall surface of the linear grooves, increasing the effect of magnetic domain refining. Therefore, the groove depth is preferably deep. On the other hand, when forming linear grooves by etching, if the amount of electrolysis, that is, the amount of reduction of base iron by forming linear grooves increases, the magnetic flux density decreases and the hysteretic loss increases. Therefore, the amount of electrolysis is preferably small. Therefore, it is desirable to narrow the groove width in order to reduce the amount of electrolysis. In addition, if the groove shape of the linear grooves after etching is not uniform, the magnetic properties of the grain-oriented electrical steel sheet may vary. Therefore, it is preferable to form a uniform resist coating pattern to form uniform linear grooves on the surface of the steel sheet.

Patent Literature 1 describes forming a resist film pattern using a laser as a technique for forming a uniform resist film pattern to form uniform linear grooves and suppressing variation in magnetic properties of a steel sheet. That is, in the technique described in Patent Literature 1, after uniformly forming a resist film over the entire surface of the steel sheet, the laser is irradiated to areas where the resist film is not required to instantaneously gasify the resist film, and selectively remove the resist film in the irradiated portion. is to remove According to the method described in Patent Literature 1, it is expected that linear grooves of a uniform shape can be formed. Further, Patent Literature 1 describes that narrow linear grooves can be formed by setting the beam diameter of the irradiated laser beam to a small diameter and approximating the shape of the laser to a perfect circle.

Specification International Publication No. 2017/017908

However, depending on the prior art, there has been a problem that the groove width after etching becomes larger than the beam diameter even when a small-diameter beam is irradiated, and a desired groove width cannot be obtained.

The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a grain oriented electrical steel sheet in which linear grooves are formed with a desired groove width on the surface of a metal strip, and further excellent in magnetic properties.

The present inventors obtained the following knowledge as a result of repeating earnest examination in order to achieve the above-mentioned subject.

(1) In a region where the width of the groove after etching is larger than the beam diameter in a direction perpendicular to the scanning direction of the laser on the surface of the metal strip (hereinafter also referred to as the orthogonal scanning direction), the laser scanning orthogonality of the portion where the resist film has been removed The width in the direction (hereinafter also referred to as the resist film removal width) is not equal to or greater than the beam diameter (hereinafter referred to as the irradiation width) in the direction perpendicular to the scanning direction of the laser, while the resist film is degenerated by the heat of the laser. A portion (heat-affected zone) exists, and the heat-affected zone is removed during etching, causing the groove width of the linear groove to increase.

(2) When the resist film is irradiated with a laser having the same beam diameter in the laser scanning direction and the beam diameter in the orthogonal direction, that is, a beam shape close to a perfect circle, the width of the heat-affected zone after laser irradiation in the direction orthogonal to the laser scanning ( Hereafter, also referred to as a heat effect width) increases when energy is applied intensively in a short time, and decreases when energy is applied in a dispersed manner over time. Therefore, in order to reduce the heat-affected width, it is effective to reduce the laser output, but simply reducing the laser output may result in insufficient removal of the resist film. Therefore, when reducing the output of the laser, it is necessary to drop the scanning speed of the laser in order to supply sufficient energy to the resist film, but dropping the scanning speed of the laser lowers productivity. Therefore, as a method of replacing the laser output reduction, a method of changing the beam shape on the surface of the metal strip from a shape close to a perfect circle to an ellipse is effective. By making the beam shape elliptical, even with the same laser output, it is possible to prevent energy input from being dispersed over time, reducing the heat-affected width, and further increasing the groove width of the linear grooves. In order to obtain this effect, it is necessary to set the ratio of the major axis diameter to the minor axis diameter of the laser beam shape to 5.0 or more.

(3) By making the beam shape elliptical, irradiation energy is spatially dispersed, and the resist film removability deteriorates. Therefore, it is effective to use a resist film containing an inorganic compound in order to reduce the energy required for removing the resist film and to reliably remove the resist film even when a laser having an elliptical beam shape is irradiated. Removal of the resist film by the laser is achieved by gasifying the organic compound contained in the resist film, and the energy of the laser is used to gasify the organic compound. When the resist film contains an inorganic compound, when the organic compound in the resist film is gasified by laser irradiation, the inorganic compound in the resist film becomes dust and is scattered and removed. Gasification of the organic compound equivalent to the inorganic compound in the resist film energy required can be reduced. In order to reliably remove the resist film with an elliptical laser, it is necessary to set the content of the inorganic compound in the resist film to 20% by mass or more in terms of solid matter.

This indication is made based on the said knowledge. That is, the gist of the present disclosure is as follows.

[1] Forming a resist film on at least one surface of the metal strip,

Next, the resist film is irradiated with a laser while scanning in a direction transverse to the rolling direction of the metal strip to remove the resist film at a portion irradiated with the laser,

Subsequently, an etching process is performed on a portion of the metal strip from which the resist film is removed to form a linear groove, a linear groove forming method,

The resist film contains 20% by mass or more of an inorganic compound in terms of solid content,

On the surface of the metal strip, the laser has an elliptical beam shape in which the ratio of the major axis diameter to the minor axis diameter is 5.0 or more, and the beam diameter in the scanning orthogonal direction is 10 μm or more and 100 μm or less.

[2] The linear groove formation method according to [1] above, wherein the irradiation energy of the laser is 30 J/m or less.

[3] Hot rolling is performed on a steel slab to obtain a hot rolled steel sheet,

Next, the hot-rolled steel sheet or the hot-rolled annealed sheet obtained by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing is subjected to cold rolling once or twice or more with intermediate annealing interposed therebetween to obtain a cold-rolled steel sheet,

Subsequently, primary recrystallization annealing is performed on the cold-rolled steel sheet to obtain a primary recrystallized sheet,

Subsequently, as a method for producing a grain-oriented electrical steel sheet, by subjecting the primary recrystallized sheet to secondary recrystallization annealing to obtain a secondary recrystallized sheet,

A method for producing a grain-oriented electrical steel sheet, wherein linear grooves are formed on at least one side of a steel sheet after hot rolling by the linear groove forming method described in [1] or [2] above.

According to the present disclosure, it is possible to provide a grain oriented electrical steel sheet in which linear grooves are formed on the surface of a metal strip with a desired groove width and further excellent in magnetic properties.

1 is a diagram showing an outline of laser irradiation.
Fig. 2 is a diagram showing the relationship between the groove width of the linear groove and the iron loss W _17/50 .
Fig. 3 is a diagram showing the relationship between the long and short axis ratio of the laser beam and the groove width after etching.
4 is a diagram for explaining a method for measuring a resist film removal width.
Fig. 5 is a diagram showing the relationship between the inorganic compound content of the resist film and the ratio of the resist film removal width to the diameter in the direction orthogonal to laser scanning.

First, an experiment that led to the development of the present disclosure will be described. In addition, in the following description, "%" means "mass %" unless otherwise specified. In addition, in this specification, the numerical range expressed using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

<Experiment 1>

As shown in Fig. 1, a resist film (solid content composition: aqueous alkyd resin 36%, melamine resin 1%, Ti-containing oxide 20%, aluminum-containing oxide 40%, other (pigment, leveling agent) 3%) is formed on the surface Cold-rolled steel sheet with a thickness of 0.23 mm (C: 0.05%, Mn: 0.10%, P: 0.004%, S: 0.001%, Al: 0.008%, N: 45 ppm, Ti + Nb + V + Zr + Ta < 0.001 %) in the direction of the arrow, laser irradiation was performed by scanning the laser irradiation device in a direction orthogonal to the rolling direction (steel plate traveling direction in the drawing), and the resist of the laser irradiation portion 40 was removed. In addition, the cold-rolled steel sheet is obtained by subjecting a steel slab to hot rolling to obtain a hot-rolled steel sheet, and then cold-rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet. The laser irradiation was repeated at intervals of 5 mm in the rolling direction. In addition, a fiber laser was used as the laser, and the beam diameter (Bt in the drawing) in the scanning orthogonal direction was changed to 5 to 300 μm on the surface of the steel sheet by changing the fiber of the laser irradiation device. As the laser, a single mode fiber laser was irradiated by a galvano scanner method. Laser irradiation energy: 25 J/m, a scanning width of 200 mm, and a scanning interval of 5 mm in the rolling direction of the steel sheet were implemented. In all conditions, the resist film of the laser irradiation area was completely removed.

In addition, the beam diameter in the scanning orthogonal direction of the laser was determined as follows. Using a commercially available CCD camera-type fixed beam profiler, the intensity profile of the beam in the direction orthogonal to the scanning direction of the laser is measured on the surface of the steel plate, and the beam intensity in the beam profile is 0.135 times the maximum beam intensity. The profile width between points was made into the beam diameter in the scanning orthogonal direction.

Next, an electrolytic etching treatment was performed on the cold-rolled steel sheet from which this resist film was removed. Subsequently, primary recrystallization annealing was performed on the cold-rolled steel sheet after the electrolytic etching treatment to obtain a primary recrystallized sheet, and an annealing separator was applied to both sides of the primary recrystallized sheet. The primary recrystallized plate after application of the annealing separator was subjected to secondary recrystallization annealing concurrently with the formation of a forsterite film to obtain a secondary recrystallized plate. Next, after flattening annealing was given to the secondary recrystallized plate, tension film formation was performed to manufacture a grain-oriented electrical steel sheet (product sheet). Using the grain-oriented electrical steel sheet, the relationship between the groove width of the linear groove and the iron loss was investigated.

Regarding the iron loss, here, the iron loss W _17/50 at a magnetic flux density of 1.7 T and an excitation frequency of 50 Hz was evaluated by a single plate magnetic tester in accordance with JIS C 2556. For the measurement of iron loss, magnetism was measured before groove processing (before electrolytic etching), and a grain-oriented electrical steel sheet having a magnetic flux density B ₈ of 1.90 T was selected and used. Further, the depth (groove depth) of the linear grooves formed by electrolytically etching the grain-oriented electrical steel sheet in the sheet thickness direction was adjusted to be the same for all grain-oriented electrical steel sheets by adjusting the electrolytic etching processing time. Regarding the groove width of the linear grooves of the grain-oriented electrical steel sheet, the height of the lowest part of the groove when three-dimensionally measured using a confocal laser microscope and the height profile in the rolling direction was defined as "height 0%" and the height of the rolling surface. When the average value of is taken as "height 100%", the distance in the rolling direction at the position of "height 95%" with the lowermost part of the groove in between is taken as the groove width, and the groove width is measured at 10 points at intervals of 1 mm in the sheet width direction, Measured by averaging.

2 shows the results. It can be seen that iron loss is good when the groove width is 10 to 100 μm. It is considered that the reason why the iron loss increases as the groove width increases is that the hysteresis loss increases with the increase in the amount of electrolysis. On the other hand, it is considered that the reason why the iron loss is deteriorated when the groove width is too narrow is that magnetic domain coupling occurs and the effect of magnetic domain refining is reduced. Since the groove width of the linear groove almost coincides with the beam diameter (Bt in Fig. 1) in the direction orthogonal to the scanning of the laser, setting the beam diameter in the direction perpendicular to the scanning of the laser to be 10 to 100 µm reduces iron loss know what's important.

<Experiment 2>

Next, the relationship between the long-short axis ratio of the beam diameter in the direction orthogonal to the scanning of the laser and the groove width of the linear groove after etching was investigated. In this experiment, an oscillator with a laser beam diameter of 100 μm was used, and a cylindrical lens was used to convert the beam shape on the steel plate to an elliptical shape. Then, the steel sheet was irradiated with the laser so that the major axis direction of the beam shape was parallel to the laser scanning direction and the minor axis direction was perpendicular to the laser scanning direction. At this time, the ratio of the major axis diameter to the minor axis diameter of the beam shape on the surface of the steel plate was set as the major minor axis ratio, and the major minor axis ratio was varied between 1 and 200. The groove width of the linear groove after etching of the cold-rolled steel sheet from which the resist film was removed by irradiating the laser at each of the long and short axis ratios was investigated. As the steel plate for forming the linear grooves, the same steel plate as in Experiment 1 was used. In addition, the cold-rolled steel sheet is obtained by subjecting a steel slab to hot rolling to obtain a hot-rolled steel sheet, and then cold-rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet. The cold-rolled steel sheet after the etching treatment was subjected to primary recrystallization annealing to obtain a primary recrystallized sheet, and then an annealing separator was applied to both surfaces of the primary recrystallized sheet. The primary recrystallized plate after application of the annealing separator was subjected to secondary recrystallization annealing concurrently with the formation of a forsterite film to obtain a secondary recrystallized plate. Next, after flattening annealing was given to the secondary recrystallized plate, tension film formation was performed to manufacture a grain-oriented electrical steel sheet (product sheet). In addition, laser irradiation energy in laser irradiation, scanning width, and scanning interval in the rolling direction of the steel sheet were carried out under the same conditions as in Experiment 1.

3 shows the results. When the ratio of the long to short axis of the beam was less than 5.0, the groove width of the linear grooves after etching tended to increase. This is because when irradiating a laser with a small beam length and short axis ratio, that is, a beam shape close to a perfect circle, when the laser output is equal, a large amount of energy is injected into a narrow area in a short time, and part of the energy becomes heat in the scanning orthogonal direction It is thought that this is because it is transmitted by heat conduction and changes the resist film in the area not irradiated with laser to generate a heat-affected zone. The heat-affected zone of the resist film is inferior in adhesion to the resist film in etching compared to the unaltered portion. Therefore, since the heat-affected zone is removed from the steel sheet during etching, it is considered that the groove width after etching is larger than the beam diameter in the direction orthogonal to the laser scanning. As shown in Fig. 2, since iron loss deteriorates when the groove width of linear grooves exceeds 100 mu m, it is not desirable to increase the groove width by the heat-affected zone.

<Experiment 3>

Although an increase in the groove width of the linear groove can be prevented by using an elliptical beam, there is a concern that the resist film may not be sufficiently removed because the energy density of the beam is dispersed. Then, with the aim of reducing the irradiation energy of the laser required for the removal of the resist film, the effect of the inorganic compound content in the resist film on the removal of the resist film was investigated. An alkyd-based resin (modified alkyd resin; organic compound) and silica (inorganic compound) were mixed to prepare a resist film containing 0 to 95% by mass of the inorganic compound in terms of solid matter. The resist film thus prepared was formed on both sides of the cold-rolled steel sheet, and laser irradiation was applied to the resist film in the same manner as in Experiment 1 to remove the resist film from the laser irradiated portion. The beam shape on the surface of the steel sheet is elliptical, the minor axis diameter is 100 μm, the long axis ratio is 50, the long axis of the beam is parallel to the scanning direction, and the short axis is perpendicular to the scanning direction. Laser irradiation was carried out. After laser irradiation, the resist film removal width was measured. Here, the resist film removal width is, as shown in FIG. 4, the direction perpendicular to the rolling direction (TD ) was taken as the average value of the width d in . Then, the ratio of the resist removal width (hereinafter also referred to as the resist removal ratio) to the beam diameter in the scanning orthogonal direction of each laser (namely, the short axis diameter of the beam in this experiment was 100 μm) was determined as a percentage. As the steel plate, the same steel plate as in Experiment 1 was used. In addition, the cold-rolled steel sheet is obtained by subjecting a steel slab to hot rolling to obtain a hot-rolled steel sheet, and then cold-rolling the hot-rolled steel sheet to obtain a cold-rolled steel sheet. In addition, the laser irradiation energy in laser irradiation, the scanning width, and the scanning interval in the rolling direction of the steel plate were implemented under the same conditions as in Experiment 1.

5 shows the results. When the content of the inorganic compound was less than 20% by mass, the resist film removal rate was greatly reduced. As described above, when a resist film is irradiated with a laser, the resist film is removed by instantly gasifying the organic compound in the resist film, but the inorganic compound present in the resist film is removed by scattering as dust when the surrounding organic compounds are gasified do. Therefore, the energy required to gasify the inorganic compound in the resist film and the organic compound in the same volume becomes unnecessary. Therefore, when a resist film containing 20% by mass or more of an inorganic compound is used, the resist film can be uniformly removed even when the irradiation energy of the laser is small. If the resist removal rate is lowered, the region where the base iron is exposed (resist removal section) and the region where the resist film partially remains in the laser irradiation section are mixed, so that the etching rate of the base iron tends to become non-uniform during etching, and the groove width becomes non-uniform, resulting in magnetic It causes variation in characteristics. Therefore, it can be seen that it is important to contain 20% by mass or more of the inorganic compound in terms of solid matter in the resist film.

Based on the above result, below, embodiment of this indication is described. In addition, the following description shows one preferred embodiment of this disclosure, and this disclosure is not limited at all by the following description.

The linear groove forming method according to the present embodiment,

Forming a resist film on at least one surface of the metal strip;

Next, the resist film is irradiated with a laser while scanning in a direction transverse to the rolling direction of the metal strip to remove the resist film at a portion irradiated with the laser,

Subsequently, as a groove forming method, forming a linear groove by performing an etching treatment on a portion of the metal strip from which the resist film is removed,

The resist film contains 20% by mass or more of an inorganic compound in terms of solid content,

On the surface of the metal strip, the laser has an elliptical beam shape in which the ratio of the major axis diameter to the minor axis diameter is 5.0 or more, and the beam diameter in the scanning orthogonal direction is 10 μm or more and 100 μm or less.

In the linear groove forming method of the present embodiment, the processing of the following steps (1) to (3) is sequentially performed on the metal strip.

(1) resist film formation step;

(2) Laser irradiation process

(3) Etching process

[metal strip]

According to the linear groove forming method according to the present embodiment, when forming linear grooves on the surface of a steel sheet using etching in various types of metal strips, linear grooves having a narrow groove width can be formed in a uniform shape. For this reason, the type of metal strip used as a target for forming the linear grooves is not limited. Since the linear groove forming method according to the present embodiment is particularly useful for reducing core loss of a grain oriented electrical steel sheet, it is preferable to apply the present linear groove forming method to production of a grain oriented electrical steel sheet.

Further, in the etching treatment step described later, when performing the etching treatment, if a film other than a resist film is formed on the surface of the metal strip, there is a possibility that etching may be inhibited. Therefore, a film insoluble or sparingly soluble in an etchant or electrolyte, such as a forsterite film, an insulation film, and a tension film, is not formed on the surface of the metal strip, and the coating material for forming a resist film described later is applied directly to the surface of the metal strip. It is preferable to apply

[Resist film formation process]

First, a coating material for forming a resist film is applied to at least one surface of the metal strip, and a resist film is formed on at least one surface of the metal strip. The resist film functions as an etching resist film for preventing etching of the metal strip at the covered portion in an etching treatment step described later.

(resist film)

A resist film contains 20 mass % or more of an inorganic compound in conversion of solid content. If the content of the inorganic compound in the resist film is less than 20 mass% in terms of solid content, the resist film is not sufficiently removed when irradiated with a laser having an elliptical beam shape with a large major axis diameter ratio in the laser irradiation step described later, and the desired groove width Linear grooves cannot be formed. The inorganic compound contained in the resist film is preferably 40% by mass or more in terms of solid content. On the other hand, if the content of the inorganic compound is too large, the content of the resin component decreases, resulting in a decrease in etching resistance and making it difficult to form uniform grooves. It is preferable that it is % or less.

(inorganic compounds)

The inorganic compound is not particularly limited as long as it is known. For example, silica, magnesium oxide, Ti-containing oxide, silica, Zr-containing oxide, glass fiber, etc. can be used alone or in combination.

Solid content other than the inorganic compound of the resist film contains an organic compound as a resin component. The resin component of the resist film is preferably a thermosetting resin. As the thermosetting resin, for example, at least one selected from the group consisting of alkyd-based resins, epoxy-based resins, polyethylene-based resins, and melamine-based resins can be used. As the alkyd-based resin, a resin obtained by reacting a polymerizable vinyl monomer with an alkyd resin obtained by subjecting a polybasic acid, a polyhydric alcohol, and a fat or oil or a processed oil to a dehydration condensation reaction and optionally further reacting with a monobasic acid can be used. . As the epoxy-based resin, bisphenol-type epoxy resins, novolac-type epoxy resins, glycidyl ethers of polyhydric alcohols, and the like can be used. As the melamine-based resin, methylated melamine, butylated melamine, and the like can be used, for example.

The coating material for forming a resist film may contain a solvent as appropriate in addition to the above-mentioned solid components such as organic compounds and inorganic compounds. As the solvent, known solvents such as ethylene glycol monon-butyl ether and diethylene glycol monon-butyl ether can be used. The content of the solvent in the coating material for forming a resist film is not particularly limited, but from the viewpoint of suppressing sagging of the ink of the coating material for forming a resist film, the coating material for forming a resist film preferably has a higher viscosity.

The method of applying the coating material for forming a resist film on at least one side of the metal strip is not particularly limited and can be carried out by any method. However, the coating material for forming a resist film is applied to the surface of various rolls, It is preferable to carry out by the method of transferring the coating material for forming the resist film on the surface of a roll to the surface of a metal strip by making it contact with the surface of a metal strip. Among them, it is preferable to apply a coating material for forming a resist film to the surface of a metal strip by a gravure printing method using a gravure roll, and a coating material for forming a resist film is preferably applied to the surface of a metal strip by a gravure offset printing method using an offset roll. It is preferable to apply to In addition, in this specification, "gravure printing method" refers to the general printing method using a gravure roll, and shall also include the gravure offset printing method. In addition, in the case of using the gravure printing method, in order to make the film thickness of the resist film constant, a doctor blade is provided above the gravure roll to uniformize the amount of the coating material for forming the resist film on the surface of the gravure roll. desirable.

When the coating material for forming a resist film is applied to the metal strip, the temperature of the coating material for forming a resist film is preferably set to 40 DEG C or less in order to keep the viscosity of the coating material for forming a resist film high. On the other hand, the lower limit of the temperature of the coating material for forming a resist film when applying the coating material for forming a resist film is not particularly limited, but is preferably 20°C or higher from the viewpoint of production technology.

The weight per unit area (application amount) of the resist film is preferably 1.0 g/m 2 or more per side, and preferably 10.0 g/m 2 or less. When the resist coating has a weight per unit area of 1.0 g/m 2 or more, good resist resistance can be obtained, so that etching can be suitably performed in the etching process described later. In addition, by setting the weight per unit area of the resist film to 10.0 g/m 2 or less, the resist film can be preferably removed even when the irradiation energy of the laser is 30 J/m or less. The weight per unit area of the resist film is the value after drying the resist film and before laser irradiation, and is derived from the weight difference between the metal strip before applying the resist film and the metal strip after drying the resist film, and the area covered by the resist film.

After a coating material for forming a resist film is applied to at least one surface of the metal strip to form a resist film, the resist film is dried before an etching process described later. Preferably, the resist film is dried before laser irradiation described later. The drying method of the coating material for forming a resist film is not particularly limited, and hot air drying, vacuum drying, and the like can be used, for example. In the case of hot air drying, the drying temperature is preferably 180 to 300°C. In the case of vacuum drying, the pressure is preferably 10 Pa or less, and the drying time is preferably 5 seconds or more.

[Laser irradiation process]

Next, irradiation is performed while scanning a laser beam in a direction transverse to the rolling direction of the metal strip on which the resist film is formed. By this laser irradiation, the resist film at the portion irradiated with the laser is locally heated, gasified, and removed. As a result, a resist removal portion in which the surface of the metal strip is exposed is formed. The exposed portions of the resist removal portion are selectively etched into linear grooves in an etching treatment step described later.

(laser)

When the laser beam shape on the surface of the metal strip is close to a perfect circle, a heat affected zone is formed around the laser irradiation portion unless the laser output is reduced. Since the heat-affected zone is removed during etching, which leads to an increase in the width of the groove, forming narrow linear grooves is not preferable from the viewpoint of enhancing the iron loss reduction effect particularly in grain-oriented electrical steel sheets. Therefore, the beam shape on the surface of the metal strip (surface of the steel sheet) of the laser is made elliptical, and the laser is irradiated while scanning so that the long axis is preferably parallel to the scanning direction and the short axis is orthogonal to the scanning direction. The formation of a heat-affected zone is suppressed by dispersing the energy input by the time. In order to suppress the formation of a heat-affected zone, the ratio of the major axis to the minor axis of the beam shape is set to 5.0 or more. From the viewpoint of forming linear grooves having a desired groove width by suppressing an increase in the groove width of the linear grooves after the etching process and enhancing the iron loss reduction effect particularly in grain-oriented electrical steel sheets, the long-short axis ratio of the beam is preferably 20 or more, and 50 It is more preferable that it is more than 100, and it is still more preferable that it is 100 or more. In addition, although the upper limit of the long-short axis ratio of a beam is not specifically limited, It is preferable to set it as 100000 or less. By setting the long-short axis ratio of the beam to 100000 or less, it is possible to prevent the beam from protruding from the width end of the metal strip and further reduce the cost for protecting equipment from the protruding beam. In addition, it is preferable that the long axis direction of the beam shape and the scanning direction of the laser are parallel, but it is possible to enjoy the effect of the present disclosure even if the long axis direction is not parallel to the scanning direction. The angle formed by the long axis direction of the beam shape with respect to the scanning direction of the laser is preferably within 30°, and more preferably within 10°. As a method of making the laser beam shape elliptical on the surface of the metal strip, besides the method of using a semiconductor laser in which the emitted light becomes elliptical, a method of converting a circular laser beam into an ellipse with a cylindrical lens, or a rotational drive There is a method of making an ellipse by reflecting a laser on a polygon mirror to make it elliptical. By adjusting the irradiation angle of the laser to the surface of the metal strip, the beam shape on the surface of the metal strip can be made elliptical.

The major axis diameter relative to the minor axis diameter of the beam shape is measured as follows. First, using a commercially available CCD camera-type fixed beam profiler, the beam intensity profile in the long axis direction of the laser is measured on the surface of the metal strip, and the beam intensity in the beam profile is equal to or greater than the maximum value of the beam intensity. The profile width between two points, which is 0.135 times larger, is taken as the beam diameter in the major axis direction (long axis diameter). Next, the beam diameter in the direction of the minor axis of the laser (minor axis diameter) is also measured in the same way, and the obtained major axis diameter is divided by the minor axis diameter to obtain a major axis ratio.

The beam diameter in the direction orthogonal to the scanning of the laser is set to 10 μm or more and 100 μm or less from the viewpoint of obtaining excellent core loss characteristics particularly in grain-oriented electrical steel sheets. The beam diameter in the scanning orthogonal direction is measured as follows. Using a commercially available CCD camera-type fixed beam profiler, the intensity profile of the beam in the direction orthogonal to the scanning direction of the laser was measured on the surface of the metal strip, and the beam intensity in the beam profile was 0.135 of the maximum beam intensity. The doubled profile width between two points is taken as the beam diameter in the scanning orthogonal direction. In addition, when the major axis direction of the beam shape coincides with the scanning direction of the laser, the minor axis diameter of the beam shape becomes the beam diameter in the scanning orthogonal direction.

The larger the irradiation energy of the laser, the smaller the removal residue of the resist film, but from the viewpoint of preventing the dissolution of the metal strip and forming a more uniform shape of the linear groove, it is recommended that the irradiation energy of the laser be 40 J/m or less. Preferably, it is more preferably 30 J/m or less, and even more preferably 10 J/m or less. The lower limit of the laser irradiation energy is not particularly limited, but in order to preferably remove the resist film, the laser irradiation energy is preferably 3 J/m or more.

In addition, the type of laser can be determined from the viewpoint of productivity and, furthermore, from the viewpoint of iron loss characteristics in grain-oriented electrical steel sheets. From the viewpoint of improving the iron loss characteristics of the grain-oriented electrical steel sheet, since a narrow groove width is advantageous, it is preferable to use a laser device with high light condensing property to narrow the resist film removal width. On the other hand, from the viewpoint of productivity, it is desired to perform laser scanning at high speed. In the case of high-speed laser scanning, it is preferable to use a laser irradiation device with higher output in order to secure the energy density required for removal. Therefore, in order to achieve both beam condensing performance and laser output, it is preferable to use a single-mode fiber laser as the type of laser. The scanning of the laser is preferably performed by rotational driving of a mirror such as a galvano mirror or a polygon mirror from the viewpoint of high speed.

Many of the generally used metal strips have a sheet width of about 1 m. In order to more uniformly irradiate the laser over the entire sheet width of a metal strip having a sheet width of about 1 m, it is preferable to use two or more laser irradiation devices.

It is preferable to perform laser scanning in a straight line. In addition, the scanning direction of the laser may be a direction transverse to the rolling direction of the metal strip.

In the laser irradiation step described above, the resist film on the portion irradiated with the laser is removed by gasification of organic compounds and scattering of inorganic compounds. Therefore, after the laser irradiation step, it is preferable to use at least one of the dust collector and the exhaust gas cleaning device to recover the resist film removed by blowing or suction. It is also possible to recover the resist film removed by blowing or suction while performing laser irradiation. However, in order to prevent defocusing due to vibration of the metal strip due to blowing or suction, the air volume of the dust collector or the exhaust gas cleaning device when blowing or suction is performed while laser irradiation is performed is set to 100 m 3 /min or less. it is desirable Further, the lower limit of the air volume is not particularly limited, but from the viewpoint of favorably recovering the removed resist film, the air volume is preferably 10 m 3 /min or more.

[Etching treatment process]

After completion of the laser irradiation process, an etching process is performed to form linear grooves on the surface of the metal strip. Although the method used for etching treatment is not specifically limited, It is preferable to use at least one of chemical etching and electrolytic etching. From the viewpoint of controlling the groove depth in the plate thickness direction of the linear grooves, it is more preferable to use electrolytic etching as a method of etching treatment. When chemical etching is used as an etching treatment method, for example, an aqueous solution containing at least one selected from the group consisting of FeCl ₃ , HNO ₃ , HCl, and H ₂ SO ₄ can be used as the etching solution. In the case of electrolytic etching, for example, an aqueous solution containing at least one selected from the group consisting of NaCl, KCl, CaCl ₂ , and NaNO ₃ can be used as the etching solution (electrolytic solution).

Moreover, it is preferable to perform an etching process while stirring an etchant. By stirring the etchant, the unevenness of the temperature and material concentration of the electrolyte solution in the etching bath can be eliminated, and etching can be performed more uniformly. Moreover, by stirring the etching solution, the flow rate of the electrolyte solution in the etching bath can be increased and the etching efficiency can be improved. The method of performing the agitation is not particularly limited, but for example, mechanical agitation by an agitating member and agitation by circulating an etching solution can be used. In the case of performing mechanical stirring, it is preferable to use a resin-made stirring member in consideration of resistance to etching liquid. In the case of performing stirring by circulation, for example, an ejection port for the etching solution may be formed in the etching bath, and the etching solution may be ejected from the ejection port using a pump or the like.

When the etching treatment is performed by electrolytic etching, the metal strip can be energized by any method. For example, the metal strip can be energized by direct or indirect energization using an etching bath of a radial cell method or a horizontal cell method. The electrolysis conditions for energization may be appropriately adjusted according to the type of steel sheet to be subjected to the etching treatment, the electrolyte solution to be used, and the like, but the current density can be adjusted within the range of 1 to 100 A/dm 2 , for example.

The groove width and groove depth of the linear grooves formed by the etching process can be adjusted depending on the laser beam shape and the etching conditions. It is preferable to set it as 100 micrometers or less. Further, the depth of the linear grooves in the plate thickness direction is preferably set to 10 µm or more, and is preferably set to 40 µm or less. Here, in the linear groove formation method according to the present embodiment, since the groove width of the linear groove and the resist removal width are substantially the same, the beam diameter in the direction orthogonal to the scanning direction of the laser is preferably 10 µm or more, and 100 µm It is preferable to set it as below.

In this linear groove forming method, conditions other than the above conditions can be set in accordance with a conventional method.

In addition, in this linear groove formation method, in addition to the above-described resist film forming step, laser irradiation step, and etching treatment step, after the above-mentioned (2) laser irradiation step and before the above-mentioned (3) etching treatment step, the resist film In order to monitor the removal status of the laser beam, it is preferable to have an image capturing process in which an imaging device enlarges and captures an image of the laser irradiation unit. The imaging device supplies the captured image to the analysis unit. The analysis unit determines the resist removal ratio based on the image acquired from the imaging device and the beam diameter in the scanning orthogonal direction of the laser. The laser irradiation conditions and the like can be adjusted using this resist removal rate. In addition, the resist removal rate can be recorded and used for product management. Since the shape of the groove changes depending on the status of the removal of the resist film in the laser irradiation unit, monitoring of the status of removing the resist film can be replaced with monitoring of the width of the groove. However, since the shape of the groove is affected by other than the removal of the resist film, it is more preferable to directly monitor the status of the removal of the resist film before forming the groove.

<Production method of grain-oriented electrical steel sheet>

The linear groove formation method according to the present embodiment can be suitably applied to the production of grain-oriented electrical steel sheets. The method for producing a grain-oriented electrical steel sheet according to the present embodiment,

Hot rolling is performed on a steel slab to obtain a hot rolled steel sheet,

Next, the hot-rolled steel sheet or the hot-rolled annealed sheet obtained by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing is subjected to cold rolling once or twice or more with intermediate annealing interposed therebetween to obtain a cold-rolled steel sheet,

Subsequently, primary recrystallization annealing is performed on the cold-rolled steel sheet to obtain a primary recrystallized sheet,

Subsequently, as a method for producing a grain-oriented electrical steel sheet, by subjecting the primary recrystallized sheet to secondary recrystallization annealing to obtain a secondary recrystallized sheet,

This is a method for producing a grain oriented electrical steel sheet in which linear grooves are formed on at least one surface of a certain steel sheet after the hot rolling by the linear groove forming method described above.

When the linear groove formation method is applied to the production of grain-oriented electrical steel sheets, the metal strip to be subjected to linear groove formation may be any steel sheet after hot rolling. More specifically, the metal strip to be grooved is a hot-rolled steel sheet after hot rolling, a hot-rolled annealed sheet obtained by annealing the hot-rolled steel sheet, a cold-rolled steel sheet after cold rolling in the case of performing cold rolling once, and intermediate cold rolling. Cold-rolled steel sheet before or after intermediate annealing, or cold-rolled steel sheet after cold rolling after intermediate annealing, primary recrystallized sheet after primary recrystallization annealing, secondary recrystallization annealing after secondary recrystallization annealing It may be a secondary recrystallized version.

The component composition in the case of manufacturing the grain-oriented electrical steel sheet is not particularly limited, and may be an arbitrary component composition. From the viewpoint of reducing the iron loss of the grain-oriented electrical steel sheet, it is preferable to have a component composition containing Si in the range of 2.0 to 8.0 mass%, and also from the viewpoint of sheet passability, the component composition containing Si in the range of 2.5 to 4.5 mass% It is more preferable to

In addition, the component composition other than Si which is preferable as a component composition in the case of manufacturing a grain-oriented electrical steel sheet is as follows. Of course, it is not limited to the following component composition, and the iron loss of the steel sheet before application is surely improved by application of the present disclosure in any grain-oriented electrical steel sheet.

C: 0.01 to 0.08% by mass

C is an element necessary for improving the texture at the time of primary recrystallization, and it is preferable to contain 0.01% by mass or more in order to obtain the effect. Further, from the viewpoint of preferably reducing the C content to an amount at which self-aging does not occur in primary recrystallization annealing, the C content is preferably 0.08% by mass or less. More preferably, the content of C is 0.03% by mass or more. More preferably, the content of C is 0.07% by mass or less.

Mn: 0.005 to 1.0% by mass

Mn is an effective element for improving hot workability. In order to obtain the said effect, it is preferable to make content of Mn into 0.005 mass % or more. Also, from the viewpoint of obtaining a better magnetic flux density, the Mn content is preferably 1.0% by mass or less. More preferably, the content of Mn is 0.010% by mass or more. More preferably, the content of Mn is 0.2% by mass or less.

In addition, the basic components other than the above components of the steel material used in the production of the grain-oriented electrical steel sheet of the present disclosure are different between the case where an inhibitor is used and the case where an inhibitor is not used to cause secondary recrystallization.

In the case of using an inhibitor to cause secondary recrystallization, a component composition containing various inhibitor components is used. For example, when using an AlN-based inhibitor, it is preferable to contain Al and N within the ranges of Al: 0.01 to 0.065 mass% and N: 0.005 to 0.012 mass%, respectively. Further, when using a MnS·MnSe-based inhibitor, it is preferable to contain at least one of S: 0.005 to 0.03 mass% and Se: 0.005 to 0.03 mass%.

On the other hand, when an inhibitor is not used to cause secondary recrystallization, Al, N, S, and Se, which are inhibitor components, are Al: 0.0100 mass% or less, N: 0.0050 mass% or less, and S: 0.0050 mass%, respectively. % or less, Se: 0.0050% by mass or less.

Further, in addition to the basic components described above, in the steel material used for production of the grain-oriented electrical steel sheet according to the present embodiment, Ni: 0.03 to 1.50% by mass, in addition to the above component composition, for the purpose of further improving magnetic properties. , Sn: 0.01 to 1.50 mass%, Sb: 0.005 to 1.50 mass%, Cu: 0.03 to 3.0 mass%, P: 0.03 to 0.50 mass%, Mo: 0.005 to 0.10 mass%, and Cr: selected from 0.03 to 1.50 mass% You may contain 1 type or 2 or more types which become.

Ni is a useful element for improving the structure of a hot-rolled sheet and improving magnetic properties. In order to obtain the effect of improving the magnetic properties, the content of Ni is preferably 0.03% by mass or more. Further, from the viewpoint of preferably developing secondary recrystallized grains and improving magnetic properties, the content of Ni is preferably 1.50% by mass or less. In addition, Sn, Sb, Cu, P, Mo and Cr are elements useful for improving magnetic properties. In order to obtain the effect of improving the magnetic properties, it is preferable to contain all of these elements at or above the respective lower limits. Further, from the viewpoint of preferably developing secondary recrystallized grains, it is preferable to contain all of these elements within the above upper limit.

In the steel material used for production of the grain-oriented electrical steel sheet according to the present embodiment, remainder other than the above components may be Fe and unavoidable impurities. In addition, since C is decarburized in primary recrystallization annealing and Al, N, S, and Se are purified in secondary recrystallization annealing, these components are unavoidable impurities in the steel sheet (grain oriented electrical steel sheet) after secondary recrystallization annealing. content is reduced to a certain extent.

When producing grain-oriented electrical steel sheets, from the viewpoint of enhancing the effect of reducing iron loss, the angle of the laser scan direction with respect to the sheet width direction of the metal strip (rolling orthogonal direction TD) is preferably 40° or less. It is more preferable that the scanning direction of the laser is parallel to the sheet width direction of the metal strip (the angle of the laser scanning direction with respect to the sheet width direction of the steel sheet is 0°). In addition, it is preferable to perform laser scanning in the laser irradiation step periodically in the rolling direction of the steel sheet. In other words, it is preferable to repeatedly perform laser scanning so that resist removal portions are formed at regular intervals in the rolling direction of the steel sheet. The distance between the resist removal sections in the rolling direction of the steel sheet (hereinafter referred to as "interval between the resist removal sections") is preferably 2 mm or more, and preferably 10 mm or less. Since the spacing of the linear grooves formed by the etching process in the rolling direction (hereinafter referred to as "interval of linear grooves") is the same as the spacing of the resist removal section, the spacing of the resist removal section must be within the above range. By doing so, the spacing between the linear grooves can be set within a preferred range, and the magnetic properties of the grain-oriented electrical steel sheet can be further improved.

Example

Next, the present disclosure will be specifically described based on examples. The following examples show preferred examples of the present disclosure, and the present disclosure is not limited by the examples at all.

(Example 1)

In order to evaluate the effect of laser irradiation conditions on the shape of the linear groove and the core loss characteristics of the grain-oriented electrical steel sheet, linear grooves were formed on the surface of the cold-rolled steel sheet under a plurality of conditions. In addition, as a cold-rolled steel sheet, it contains C: 0.05 mass%, Si: 3.25 mass%, Mn: 0.01 mass%, Al: 0.029 mass%, N: 0.012 mass%, S: 0.005 mass%, and Se: 0.012 mass%. A steel slab having a composition (composition containing an inhibitor component) is hot-rolled to obtain a hot-rolled steel sheet, and then the hot-rolled steel sheet is cold-rolled to obtain a cold-rolled steel sheet having a width of 0.27 mm and a width of 1120 mm. did Thereafter, a coating material for forming a resist film was uniformly applied to the entire both surfaces of the cold-rolled steel sheet by a gravure offset printing method. As the coating material for forming a resist film, a coating material for forming a resist film containing an epoxy-modified melamine alkyd resin and 40% by mass of magnesium oxide in terms of solid content was applied. The weight per unit area (after drying) of the resist film was 3.0 g/m 2 .

After applying the coating material for forming a resist film, drying was performed at 330°C for 40 s to form a resist film on the surface of the cold-rolled steel sheet. Next, under the conditions shown in Table 1, the laser was irradiated while linearly scanning in the sheet width direction of the cold-rolled steel sheet. The scanning of the laser was performed periodically at intervals of 3.5 mm in the rolling direction of the steel sheet. In this experiment, three single-mode fiber laser irradiation devices were arranged in a row in the sheet width direction of a cold-rolled steel sheet, and laser irradiation was performed using the three irradiation devices. The laser scanning speed, irradiation energy, beam diameter in the laser scanning orthogonal direction, and laser long-short axis ratio were as shown in Table 1.

<Measurement of Resist Film Removal Width>

For the cold-rolled steel sheet after laser irradiation, the removal width of the resist film was measured. The surface of the cold-rolled steel sheet after laser irradiation was observed with an optical microscope, and the width in the rolling direction of the region where the base iron was exposed in the laser irradiation area was measured at 10 points over 1 mm in the laser scanning direction, and the average value was taken as the removal width of the resist film. . Further, if the difference between the removal width of the resist film and the beam diameter in the scanning orthogonal direction is -80% or more and +180% or less with respect to the beam diameter in the scanning orthogonal direction, the resist film is formed with a width approximately equal to the diameter of the irradiated laser. It was determined that it could be removed.

Then, electrolytic etching was performed on the cold-rolled steel sheet after laser irradiation, and linear grooves were formed on both surfaces of the cold-rolled steel sheet. As the electrolytic solution, a 25% by mass NaCl aqueous solution was used, and current density was previously adjusted so that the groove depth was 20 μm in all cold-rolled steel sheets. Electrolysis conditions were made into electrolyte solution temperature: 20 degreeC, current density: 4-24 A/dm<2>, and energization time: 2 min. After completion of the etching treatment, the resist film remaining on the front and back surfaces of the cold-rolled steel sheet was removed with an aqueous NaOH solution. The liquid temperature of the NaOH aqueous solution was maintained within the range of 50 to 70°C. After completion of the etching treatment, the cold-rolled steel sheet was subjected to water washing and surface cleaning treatment.

Thereafter, the cold-rolled steel sheet is subjected to primary recrystallization annealing at 850°C to obtain a primary recrystallized sheet, then the primary recrystallized sheet is subjected to secondary recrystallization annealing at 1000°C to obtain a secondary recrystallized sheet, and then A tensile film was formed on the secondary recrystallized plate. For the grain-oriented electrical steel sheet thus obtained, iron loss W _17/50 was measured in the same manner as in Experimental Example 1. In addition, when the iron loss W _17/50 was 0.80 W/kg or less, it was determined that the iron loss characteristics were excellent. The measurement results are listed together in Table 1.

<Measurement of groove width of linear groove>

The depth profile of linear grooves in the rolling direction was measured using a confocal laser microscope. Average value of 10 measurements in the laser scanning direction, taking the rolling surface as "height 100%" and the maximum depth of groove depth as "height 0%", taking the width in the rolling direction at the position of "height 90%" as the groove width was made into the groove width of the linear groove. Further, if the difference between the groove width of the linear groove and the beam diameter in the scanning orthogonal direction was -70% or more and +500% or less with respect to the beam diameter in the scanning orthogonal direction, it was judged that the linear groove with the desired groove width could be formed. Further, when the groove width of the linear groove was 10 μm or more and about 100 μm or less, it was judged that the groove width of the linear groove was good. The measurement results are listed together in Table 1.

As can be seen from the results shown in Table 1, in the invention examples employing the linear groove forming method within the scope of the present disclosure, linear grooves having a desired groove width and a good groove width can be formed, which is better than that of the comparative example. It can be seen that it has iron loss characteristics.

(Example 2)

In the same manner as in Example 1, a cold-rolled steel sheet before groove formation was manufactured. To the cold-rolled steel sheet, a coating material for forming a resist film in which 0 to 95% by mass of silica in terms of solid content was blended with a coating material for forming a resist film containing an aqueous alkyd resin as a main component was applied uniformly over the entire surface of the steel sheet by a gravure offset printing method. applied. The weight per unit area (after drying) of the resist film was 3.0 g/m 2 . After applying the coating material for forming a resist film, drying was performed at 330°C for 40 s. Next, the laser was irradiated while scanning in a straight line along the sheet width direction of the cold-rolled steel sheet under conditions of a scanning speed of 60 m/s, a beam irradiation energy of 30 J/m, a beam diameter of 50 μm, and a beam long-short axis ratio of 50. Laser scanning was performed periodically at intervals of 3.5 mm in the rolling direction of the cold-rolled steel sheet. In this experiment, three single-mode fiber laser irradiation devices were arranged in a row in the sheet width direction of a cold-rolled steel sheet, and laser irradiation was performed using the three irradiation devices.

Subsequently, electrolytic etching was performed on each cold-rolled steel sheet to form linear grooves on the surface of the cold-rolled steel sheet. A 25% by mass NaCl aqueous solution was used as the electrolyte solution, and current density was previously adjusted so that linear grooves with a groove depth of 20 μm were formed on all cold-rolled steel sheets. Electrolysis conditions were made into electrolyte solution temperature: 20 degreeC, current density: 4-24 A/dm<2>, and energization time: 2 min. After completion of the etching treatment, the resist film remaining on the front and back surfaces of the cold-rolled steel sheet was removed with an aqueous NaOH solution. After completion of the etching treatment, the cold-rolled steel sheet was subjected to water washing and surface cleaning treatment.

Thereafter, the cold-rolled steel sheet is subjected to primary recrystallization annealing at 850°C to obtain a primary recrystallized sheet, then the primary recrystallized sheet is subjected to secondary recrystallization annealing at 1000°C to obtain a secondary recrystallized sheet, and then A tensile film was formed on the secondary recrystallized plate. For the grain-oriented electrical steel sheet thus obtained, iron loss W _17/50 was measured in the same manner as in Experimental Example 1. In addition, when the iron loss W _17/50 was 0.80 W/kg or less, it was determined that the iron loss characteristics were excellent. The measurement results are listed together in Table 2.

As can be seen from the results shown in Table 2, in the example of the invention employing a resist film containing 20% by mass or more of an inorganic compound, linear grooves having a desired groove width and a good groove width can be formed, Comparative Example It can be seen that it has better iron loss characteristics.

10: laser irradiation device
20: metal strip
30: laser
40: laser irradiation unit

Claims (3)

Forming a resist film on at least one surface of the metal strip;
Next, the resist film is irradiated with a laser while scanning in a direction transverse to the rolling direction of the metal strip to remove the resist film at a portion irradiated with the laser,
Subsequently, an etching process is performed on a portion of the metal strip from which the resist film is removed to form a linear groove, a linear groove forming method,
The resist film contains 20% by mass or more of an inorganic compound in terms of solid content,
On the surface of the metal strip, the laser has an elliptical beam shape in which the ratio of the major axis diameter to the minor axis diameter is 5.0 or more, and the beam diameter in the scanning orthogonal direction is 10 μm or more and 100 μm or less. According to claim 1,
A linear groove forming method, wherein the irradiation energy of the laser is 30 J/m or less. Hot rolling is performed on a steel slab to obtain a hot rolled steel sheet,
Next, the hot-rolled steel sheet or the hot-rolled annealed sheet obtained by subjecting the hot-rolled steel sheet to hot-rolled sheet annealing is subjected to cold rolling once or twice or more with intermediate annealing interposed therebetween to obtain a cold-rolled steel sheet,
Subsequently, primary recrystallization annealing is performed on the cold-rolled steel sheet to obtain a primary recrystallized sheet,
Subsequently, as a method for producing a grain-oriented electrical steel sheet, by subjecting the primary recrystallized sheet to secondary recrystallization annealing to obtain a secondary recrystallized sheet,
A method for producing a grain-oriented electrical steel sheet, wherein linear grooves are formed on at least one side of a steel sheet after hot rolling by the linear groove forming method according to claim 1 or 2.

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